Lost Communications With BCM (GM)
The C0291 code means the vehicle's onboard diagnostic system has detected: Lost Communications With BCM (GM). This is a serious severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- moderate
- Estimated cost
- $50 - $600 (power, ground, or CAN wiring to the named module most often)
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What Are the Symptoms of C0291?
- Multiple warning lights on
- Functions shared between modules degraded
What Causes C0291? (Most Likely First)
- Fault in the module communication component this code names (Lost Communications With BCM) High
- Damaged wiring or a corroded connector in that circuit - road-splash zones corrode connectors High
- Failed related sensor or actuator Moderate
- Control module fault Low
Can I Still Drive with C0291?
Yes, but fix soon. C0291 is rated serious severity. It is not an immediate stop-driving fault, but it will not clear itself — book the repair rather than ignoring the light.
Frequently Asked Questions
What does C0291 mean?
C0291 is a chassis code used primarily by GM vehicles: Lost Communications With BCM. It concerns the module communication system.
Can I keep driving with C0291?
Generally yes; the module communication system may be degraded. Diagnose soon, and treat any brake- or steering-related behavior change as urgent.
Is C0291 the same on every make?
The decimal C0xxx range is dominated by GM's assignments (Chevrolet, GMC, Buick, Cadillac). Other makes may use this ID differently - if your vehicle is not a GM product, verify the meaning in your make's service information.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose C0291?
-
Read the code with a GM-capable scan tool and note the symptom byte/subcode if shown.
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View live data for the named circuit (e.g. all four wheel speeds while rolling for wheel-speed codes).
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Inspect the circuit's wiring and connectors - chassis harnesses live in the splash zone and corrode first.
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Follow the GM pinpoint test for C0291 before replacing components.
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
Which Vehicles Commonly Get C0291?
- Chevrolet, GMC, Buick, Cadillac (GM chassis code range)
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